Infusion pumps for delivering fluid to a patient are well known in the art. Two general categories of infusion pumps known in the art are ambulatory pumps and large volume parenteral (LVP) pumps. These pumps deliver fluid to a patient through tubing at higher accuracies than gravity drip tubing delivery systems.
LVP pumps are relatively large infusion pumps that can provide a fluid to a patient for 24 hours or more on a single battery charge, or indefinitely from an AC power connection. They operate on standard IV polyvinyl chloride (PVC) tubing. This obviates the need for changing IV tubing sets when a decision has been made to change from a drip tubing delivery system to the more accurate infusion pump system. Most available LVP pumps completely collapse the PVC tubing during operation to ensure that there is no free flow to the patient or back flow to the fluid reservoir. This leads to very high power consumption when using standard tubing. Thus, a battery capable of powering the pump for 24 hours is very heavy and bulky. A patient receiving fluid from an LVP pump must stay within reach of a power cord, or push a wheeled stand with the LVP pump and battery mounted on it. In addition, fully collapsing the tubing deforms the tubing. The tubing cross section becomes more elliptical the longer the pump operates on it. Less fluid is discharged from the tubing as the cross section becomes more elliptical, leading to negative flow rate errors. The pump rate accuracy decays proportional to the amount of time an individual tubing set is used to deliver fluid to a patient. An example of an LVP infusion pump is shown in U.S. Pat. No. 4,653,987 (Tsuji et al.).
Ambulatory pumps are smaller infusion pumps that can be attached to a patient's belt, allowing them to move around without a bulky LVP pump. However, there are several drawbacks in comparison to the LVP pump. To reduce the weight to a level where a patient can carry the pump, the size of the battery is reduced considerably. The reduced battery cannot provide the power required to completely collapse standard PVC tubing. Instead, many ambulatory pumps require the use of special dedicated IV sets, or special silicon tubing threaded through a cassette to be inserted into the pump. This specialized equipment increases the cost of using the pumps. Even with special dedicated IV sets or silicon tubing and cassettes, many ambulatory pumps can only provide fluid to a patient for a few hours on a single battery charge. An example of an infusion pump that requires a dedicated IV set is shown in U.S. Pat. No. 5,772,409 (Johnson). An example of an ambulatory infusion pump that requires silicon tubing and cassettes is shown in U.S. Pat. No. 5,791,880 (Wilson).
Another problem with the infusion pumps currently in the art is the danger of free flow of fluid when the tubing is inserted or removed from the pump. An occluder is used to completely collapse the tubing while the tubing is outside the pump. The occluder is disengaged when the tubing is installed in the pump. The tubing is occluded again before the tubing is taken out of the pump. However, there is no means currently in the art to ensure that the tubing is occluded before the tubing is installed into or removed from the pump. Thus, the tubing may accidentally become unoccluded while the tubing is outside the pump, allowing fluid to flow freely to the patient. This overdose of fluid may be harmful or even lethal.
Clearly, then, there is a longfelt need for an ambulatory infusion pump that utilizes standard PVC tubing, operates for approximately 24 hours on one battery charge, and can prevent free flow of fluid into the patient.